Ambient Vibration Data Analysis for Structural Identification and Global Condition Assessment

System identification is an area which deals with developing mathematical models to characterize the input-output behavior of an unknown system by means of experimental data. Structural health monitoring (SHM) provides the tools and technologies to collect and analyze input and output data to track the structural behavior. One of the most commonly used SHM technologies is dynamic testing. Ambient vibration testing is a practical dynamic testing method especially for large civil structures where input excitation cannot be directly measured. This paper presents a conceptual and reliable methodology for system identification and structural condition assessment using ambient vibration data where input data are not available. The system identification methodology presented in this study is based on the use of complex mode indicator functions (CMIFs) coupled with the random decrement (RD) method to identify the modal parameters from the output only data sets. CMIF is employed for parameter identification from the unscaled multiple-input multiple-output data sets generated using the RD method. For condition assessment, unscaled flexibility and the deflection profiles obtained from the dynamic tests are presented as a conceptual indicator. Laboratory tests on a steel grid and field tests on a long-span bridge were conducted and the dynamic properties identified from these tests are presented. For demonstrating condition assessment, deflected shapes obtained from unscaled flexibility are compared for undamaged and damaged laboratory grid structures. It is shown that structural changes on the steel grid structure are identified by using the unscaled deflected shapes.     

A Study on the Evaluation of Heating and Cooling Energy Efficiency in Residential Buildings for Climatic Zones of Turkey

In Turkey, most of the common type projects of mass production residential buildings are being developed and constructed by TOK1 （Housing Development Administration of Turkey）. These buildings, in which energy efficient approach has been disregarded for years, cause to gradually increase on heating and cooling energy consumptions. In regards to national economics, it is essential to evaluate energy efficiency and to develop suggestions to decrease energy consumptions in residential buildings. To achieve appropriate solutions, cost evaluation also becomes necessary. Therefore, this paper aims to introduce a study which serves the purpose of producing a choice of energy efficient solutions in order to reduce energy consumptions and energy cost. In this study, different heating and cooling energy efficient scenarios have been developed for a selected residential building, constructed by TOKI, for climatic zones of Turkey. For each scenario, energy simulations have been executed by means of the simulation program--DesignBuilder, the user-friendly visual interface of EnergyPlus, and cost analysis has been carried out by using the net present value and discounted payback period method. As a result, energy and cost effective solutions have been presented and discussed for different climatic zones.     

An I/Q mixer with an integrated differential quadrature all-pass filter for on-chip quadrature LO signal generation

A down-conversion in-phase/quadrature (I/Q) mixer employing a folded-type topology, integrated with a passive differential quadrature all-pass filter (D-QAF), in order to realize the final down-conversion stage of a 60 GHz receiver architecture is presented in this work. Instead of employing conventional quadrature generation techniques such as a polyphase filter or a frequency divider for the local oscillator (LO) of the mixer, a passive D-QAF structure is employed. Fabricated in a 65 nm CMOS process, the mixer exhibits a voltage gain of 7-8 dB in an intermediate frequency (IF) band ranging from 10 MHz-1.75 GHz. A fixed LO frequency of 12 GHz is used to down-convert a radio frequency (RF) band of 10.25-13.75 GHz. The mixer displays a third order input referred intercept point (IIP₃) ranging from -8.75 to -7.37 dBm for a fixed IF frequency of 10 MHz and a minimum single-sideband noise figure (SSB-NF) of 11.3 dB. The mixer draws a current of 6 mA from a 1.2 V supply voltage dissipating a power of 7.2 mW.     

Investigation of Structural Defects in CdZnTe Detector-Grade Crystals

We investigated structural defects in CdZnTe detector-grade crystals grown under different conditions. Here, we report our findings from high-resolution electron microscopy [transmission electron microscopy (TEM) and scanning TEM (STEM)] and scanning electron microscopy integrated with energy-dispersive x-ray spectroscopy to characterize the material’s structural and chemical composition. Combining these techniques gave us important information about the defects, their concentration, and the elemental composition of the CdZnTe crystals. Our experimental observations demonstrated some distinct nanostructural defects in the crystals that may play a major role in device performance.     

Diverse biotechnological applications of multifunctional titanium dioxide nanoparticles: An up‐to‐date review

Titanium dioxide (TiO₂) nanoparticles (NPs) are one of the topmost widely used metallic oxide nanoparticles. Whether present in naked form or doped with metals or polymers, TiO₂ NPs perform immensely important functions. However, the alteration in size and shape by doping results in improving the physical, chemical, and biological behaviour of TiO₂ NPs. Hence, the differential effects of various TiO₂ nanostructures including nanoflakes, nanoflowers, and nanotubes in various domains of biotechnology have been elucidated by researchers. Recently, the exponential growth of research activities regarding TiO₂ NPs has been observed owing to their chemical stability, low toxicity, and multifaceted properties. Because of their enormous abundance, plants, humans, and environment are inevitably exposed to TiO₂ NPs. These NPs play a significant role in improving agricultural attributes, removing environmental pollution, and upgrading the domain of nanomedicine. Therefore, the currently ongoing studies about the employment of TiO₂ NPs in enhancement of different aspects of agriculture, environment, and medicine have been extensively discussed in this review.     

Investigation of the effect of zeolite,bentonite, and basalt fiber as natural reinforcing materials on the material properties of PPS and CF-reinforced PPS

This study was performed to expand the usage area of phenylene sulfide (PSS) by reducing its cost without deteriorating the material properties. For this purpose, mechanical, thermo-mechanical and abrasion tests were conducted to composite materials obtained by adding carbon fiber (CF), basalt fiber (BF), zeolite, and bentonite into PPS, and the effects of additive type and ratio were examined. For the test samples, fabricated by the melt blending, the fiber content was 10 wt.%, while zeolite, and bentonite ratios were 1, 5, and 10 wt.%. According to tensile and abrasion test results, zeolite, and bentonite improved the properties of fiber-reinforced PPS by showing a synergistic effect. It has been demonstrated in this research that the cost of fiber-reinforced PPS matrix composites, which are widely used in advanced engineering applications, can be reduced by using natural minerals zeolite and bentonite without sacrificing material properties. Findings obtained from mechanical and wear tests, revealed that the composition containing 10, 10, and 80 wt.%, zeolite, CF, and PPS, respectively, exhibited optimum material properties. BF for PPS has been shown to be an alternative reinforcement to CF, as it exhibits the lowest wear rate and better interacts with particles in the matrix.     

Modelling and Simulation of Design Variants for the Development of 4H-SiC Thyristors

Silicon - Wide band-gap semiconductor materials such as SiC have created a contemporaneous worldwide interest in high power electronic applications and boosted the research possibilities....